1. The Field of the Invention
The present invention relates generally to a resonator pumping system, particularly useful as an accurate drug delivery system, and having a resonating structure coupled to a fluid pump for pumping fluid.
2. The Background Art
Many applications or situations require accurately pumping or metering relatively small quantities of fluid. For example, IV pumps have been developed to accurately meter or control medicament from an IV bladder to an IV needle for treating a patient. The intravenous administration of fluids to patients is a well-known medical procedure for, among other things, (i) providing life sustaining nutrients to patients whose digestive tracts are unable to function normally due to illness or injury, (ii) supplying antibiotics to treat a variety of serious infections, (iii) delivering analgesic drugs to patients suffering from acute or chronic pain, (iv) administering chemotherapy drugs to treat patients suffering from cancer, etc.
The intravenous administration of drugs frequently requires the use of an IV pump connected or built into a so-called IV administration set including, for example, a bottle of fluid to be administered and typically positioned upside down, a sterile plastic tubing set, and a pump for pumping fluid from the bottle through the IV set to the patient. Other mechanisms may be included to manually stop the flow of fluid to the IV feeding tube and possibly some monitoring devices.
Current IV pumps generally are of two basic types: electronic pumps and disposable non-electronic pumps. Although the electronic pumps have been significantly miniaturized and do include some disposable components, they are nevertheless generally high in cost, require frequent maintenance with continued use, and may be difficult for a layman to operate if, for example, self treatment is desired.
The disposable non-electric pumps generally consist of small elastomeric bags within a hard shell container, in which the bags are filled with IV solution under pressure. The pressure generated by the contraction of the elastomeric bag forces the IV solution through a fixed orifice at a constant flow rate into the patient""s vein. Although these pumps are much less expensive than the electronic pumps and eliminate the need for maintenance (since they are discarded after every use), their drawbacks include the lack of monitoring capability, the lack of the ability to select different flow rates, limited fluid capacity, and still relatively high cost for a disposable product.
Disadvantages with many prior art IV pumps includes their relatively large size, complexity, and cost. Such IV pumps are typically bulky, complicated, and costly to produce and use.
It has been recognized that it would be advantageous to provide a pump system which would allow precise pumping or metering of fluids, such as medicament, including IV fluids, and other application where the fluid is more concentrated, such as insulin, PCA, and chemotherapy. In addition, it has been recognized that it would be advantageous to provide such a pump system which is cost effective to produce and use, and which may be disposable. In addition, it has been recognized that it would be advantageous to provide such a pump system which is small and controllable.
The invention provides a resonator pump system including a resonating structure configured for resonating, and a fluid pump coupled to and driven by the resonating structure. The fluid pump preferably includes a cavity having a fluid inlet and a fluid outlet, and a piston movably disposed within the cavity and operatively coupled to the resonating structure. An energy source is operatively coupled to the resonating structure for maintaining resonant reciprocation.
In accordance with one aspect of the present invention, the resonating structure reciprocates at a relatively high frequency, such as between 200 Hz to 2 Khz, and the fluid pump is relatively small, having a cavity or piston diameter of between 100 to 1000 microns.
In accordance with another aspect of the present invention, the pump system includes a sensor for sensing the resonation of the resonating structure and producing a sensor signal. The energy source may include a driver which is responsive to the sensor signal for applying a force to the resonating structure to maintain the resonance. A controller may be coupled to the driver and the sensor for controlling the amplitude or frequency of the resonating structure.
In accordance with another aspect of the present invention, the fluid pump is mechanically coupled to a moving portion of the resonating structure by a transmission arm coupled to and between the resonating structure and the fluid pump. The transmission arm may be a flexible arm rigidly coupled to both the pump and the structure. Alternatively, the transmission arm may be a rigid arm pivotally coupled to both the pump and the structure.
In accordance with one embodiment of the present invention, the resonating structure includes a spring element coupled to a mass, and configured for linear motion with respect to the base.
In accordance with another embodiment of the present invention, the resonating structure includes an elongated and flexible spring element coupled to a mass, and configured for arcuate motion with respect to the base.
In accordance with another embodiment of the present invention, the resonating structure includes a piezoelectric element configured for bending under an applied electric field.
In accordance with another embodiment of the present invention, the fluid pump comprises first and second fluid pumps on opposite sides of the resonating structure to achieve a substantially constant fluid flow.
In accordance with another embodiment of the present invention, the fluid pump includes a cavity disposed proximate the spring element, and a piston directly connected to the spring element.
In accordance with another embodiment of the present invention, the system includes a spool valve fluidly coupled to the fluid pump, and a second resonating structure coupled to the spool valve, and configured for resonating 90 degrees out of phase from the first resonating structure.
In accordance with another aspect of the present invention, a plurality of resonating structures are coupled to a plurality of fluid pumps with the fluid pumps being coupled in series to increase pressure. In addition, fluid pumps may be coupled in parallel to increase flow.
In accordance with another embodiment of the present invention, the system may include first and second flat layers, and a third layer sandwiched between the first and second layers. The third layer is patterned with openings to form both the resonating structure and the fluid pump.
The fluid pump and resonating structure may be inserted into an IV line in order to pump or meter medicament to an IV needle.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the invention without undue experimentation. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.